The present invention relates to a flushing position controller incorporated in an ink-jet recording apparatus and a flushing method used for the same. More particularly, the present invention relates to an ink-jet recording apparatus comprising an ink-jet recording head which is mounted on a carriage so as to travel in the widthwise direction of recording paper and which forms an image on a recording medium by ejecting jets of ink droplets via nozzle orifices, and a flushing region provided on the path along which the recording head travels for receiving ink droplets to be jetted when a flushing drive signal is supplied to the recording head; a flushing method for use with such an ink-jet recording apparatus; and a flushing position controller for use with the ink-jet recording apparatus.
Ink-jet recording apparatus can print small dots at a comparatively low noise level at high density, and hence they have recently been used in many printing applications, including color printing.
Such an ink-jet recording apparatus comprises an ink-jet recording head which receives ink supplied from an ink cartridge, and a paper feeder for feeding recording paper relative to the recording head. Text or an image is recorded on the recording paper by causing the recording head to eject ink droplets toward the recording paper while the recording head travels together with a carriage in the widthwise direction of the recording paper.
For example, a black recording head for ejecting black ink and a color recording head capable of ejecting various colors of ink, such as yellow, cyan, and magenta, are mounted on a single recording head. The ink-jet recording apparatus enables full-color printing through use of black ink and other colors of ink, as well as printing of text, by means of changing the proportions of color inks to be ejected.
Such an ink-jet recording head performs a printing operation by ejecting ink, which is pressurized in a pressure generating chamber, in the form of ink droplets by way of nozzles. The ink-jet recording head suffers problems such as printing failures, which are caused by an increase in the viscosity of ink due to evaporation of a solvent by way of nozzle orifices, solidification of ink, adhesion of dirt or dust to the nozzles, or mixing of air bubbles into ink.
In order to prevent the printing failures, the ink-jet recording apparatus is equipped with a capping member for sealing the nozzle orifices of the recording head while the recording apparatus is in a non-printing mode, and a cleaning device for cleaning a nozzle plate, as required.
The capping member acts as a cap for preventing ink from being dried by way of the nozzle orifices while the recording apparatus is in a non-printing mode. Further, in the event that the nozzle orifices become clogged, the capping member seals the nozzle plate and eliminates clogging in the nozzle orifices caused by solidification of ink or an ink ejecting failure caused by mixing of air bubbles into the ink flow channel, by suctioning ink by way of the nozzle orifices and by means of negative pressure imparted by a suction pump.
Forced discharging operation, which is performed in order to eliminate clogging in the recording head or air bubbles mixed into the ink flow channel, is usually called cleaning operation. The cleaning operation is performed when a printing operation is resumed after the recording apparatus has remained in an idle mode for a long period of time or when the user actuates a cleaning switch for eliminating degradation in the quality of a recorded image. The cleaning operation involves removal of ink droplets from the recording head by means of negative pressure applied through suction, and wiping of the surface of the recording head by means of a wiping blade formed from rubber or an elastic plate.
The capping member also has a capability of ejecting ink droplets by application to the recording head of a drive signal that is irrelevant to printing. This function is usually called flushing operation. The flushing operation is performed at predetermined cycles for the purposes of: recovering meniscuses, which are formed irregularly in the vicinity of nozzle orifices of the recording head as a result of wiping action of the wiping blade during the cleaning operation; discharging mixed ink which has flowed back from the nozzles as a result of wiping operation; and preventing clogging in the nozzle orifices from which a small amount of ink droplets is ejected during a printing operation, which would otherwise be caused by an increase in the viscosity of ink.
The schematic configuration of an ink-jet recording apparatus capable of effecting a flushing operation and a cleaning operation such as those mentioned previously will now be described by reference to FIG. 23.
In FIG. 23, reference numeral 1 designates a carriage. The carriage 1 is configured so as to travel back and forth along a carriage shaft 4 which is horizontally supported by side frames 2 and 3, by way of movement of a timing belt driven by an unillustrated carriage motor.
An ink-jet recording head 5 is mounted on the carriage 1 so as to face downward, and a black ink cartridge 6 for supplying black ink to the recording head 5 and a color ink cartridge 7 are removably mounted on the top of the carriage 1.
A paper guide member 8 is situated below the recording head 5 and extends in the same direction as that in which the recording head 5 scans, and recording paper 9 serving as a recording medium is placed on the paper guide member 8. The recording paper 9 is fed in the direction orthogonal to the scanning direction of the recording head 5, by means of an unillustrated paper feeder.
Reference numeral 10 designates a capping member disposed in a non-print region (i.e., the home position). When the recording head 5 has moved to a position immediately above the non-print region, the capping member 10 can seal a nozzle plate serving as a nozzle forming surface of the recording head 5.
A suction pump 11 is disposed below the capping member 10 so as to impart negative pressure to the interior space of the capping member 10.
The capping member 10 acts as a cap for preventing drying of the nozzle orifices of the recording head 5 while the ink-jet recording apparatus is in a non-print mode, and as a member for sucking ink by imparting negative pressure supplied from the suction pump 11 to the recording head 5.
A wiping member 12 formed from rubber or an elastic plate is provided in the vicinity of the capping member 10. When the carriage 1 travels back and forth toward the capping member 10, the wiping member 12 wipes a nozzle forming surface of the recording head 5.
A flushing region 13A is provided in another non-print region which is located opposite the non-print region where the capping member 10 is provided, with a center print region located therebetween.
The flushing region 13A is defined by an aperture 13a formed in the paper guide member 8.
An ink-absorbing member 14 is disposed behind the aperture 13a (or on the inner bottom of the recording apparatus) and doubles as a member for absorbing and retaining the ink discharged by the suction pump 11 from the interior space of the capping member 10. The ink-absorbing member 14 is housed in an ink-absorbing material housing case disposed along the paper guide member 8; i.e., a waste-ink tank 15.
In the recording apparatus, nozzles are periodically flushed in order to prevent ejecting failures, which would otherwise be caused by an increase in the viscosity of ink remaining in the nozzles which are not used during the printing operation.
Particularly, a recent large-scale model of the ink-jet recording apparatus performs flushing of ink at an average rate of several tens of droplets per nozzle every several seconds.
After a cleaning operation, at the beginning of a printing operation, or periodically during a printing operation, thousands of droplets or even tens of thousands of droplets of ink may be ejected.
The recording head may be flushed within the capping member 10 or in the flushing region 13A constituted of the aperture formed in the paper guide member 8.
Particularly, the recording head is flushed within the flushing region in order to prevent an overflow of ink, which would otherwise be caused when ink droplets are continuously ejected after the capping member 10 has already been filled with ink.
As mentioned above, the related ink-jet recording apparatus is required to temporarily suspend a printing operation in order to flush the recording head, move the carriage to the capping member or the flushing region, return the carriage to the position where the printing operation was interrupted, after flushing of the recording head is completed, and resume the printing operation.
Because of these requirements, the related recording apparatus encounters technological problems; i.e., a deterioration in throughput associated with the flushing operation; and an increase in print time.
If the recording head is to be flushed while situated at the non-print region opposite the capping member, the carriage must temporarily travel to the capping member, thus considerably deteriorating throughput.
Since the ink-absorbing member receives ink ejected by the recording head, the ink-absorbing member must be placed in a position opposite the flushing region. However, in some cases the ink-absorbing member cannot be disposed opposite the flushing region, because of a limitation imposed by the layout of other components.
Further, there exists demand for a further reduction in the size of the ink-absorbing member in order to make the recording apparatus compact.
There has also been recently provided a model of ink-jet recording apparatus which is pre-installed with a sequence for flushing a recording head within a flushing region formed opposite the traveling direction of the carriage, without moving the recording head to the capping member in order to improve throughput.
A sequence for flushing a recording head in a flushing region other than the capping member is employed in a case where a time interval between required periodic flushing operations is short, where considerable time is required to move the carriage across paper of large size, or where the direction of printing is out of synchronism with the timing at which flushing is effected.
As shown in FIG. 23, if the aperture 13a is formed in the paper guide member 8 as the flushing region, the nozzle forming surface of the recording head 5 is spaced several centimeters away from the ink-absorbing member 14, thus inevitably involving an increase in the distance over which ink is to be ejected.
Some of ink droplets ejected from the nozzle orifices of the recording head turn into mist as a result of air resistance and are suspended in air before arrival at the ink-absorbing member 14, thus staining the surroundings.
Ink droplets ejected from the nozzle orifices are electrically charged to a considerably degree. The ink droplets are affected by the electrostatic charge developed in a drive section of the recording apparatus and are accelerated by an air flow induced by an exhaust fan disposed for preventing an increase in the internal temperature of the recording apparatus or an air flow resulting from movement of the carriage, thus staining as well the (external) area surrounding the recording apparatus.
In a recent recording apparatus which controls the quantity of single ink droplets so as to form the smallest-possible ink droplets in order to implement high picture quality, the foregoing problems become more pronounced.
A conceivable measure for preventing the problems is to place waste-fluid absorbing material in proximity to the recording head. However, a mechanism, such as a paper feed roller, is usually disposed in an area within a range of carriage travel facing the head, thus making it difficult to ensure a sufficient capacity for the mechanism. Further, the waste-fluid absorbing material is selected so as to have higher capability of absorbing a waste-fluid (i.e., ink). Therefore, if ink droplets are sprayed directly onto the waste-fluid absorbing material during flushing operation, the waste-fluid absorbing material is susceptible to clogging. Further, such a waste-fluid absorbing material is slow to absorb ink.
To solve such a problem, the present inventors of the invention proposed that a slant member for guiding the ejected ink into the ink-absorbing member 14 be interposed between the aperture 13a formed in the paper guide member 8 and the ink-absorbing member 14.
Even in this case, the ink ejected from the recording head 5 tends to solidify on the surface of the slant member, thus raising the new technical problems of the thus-solidified ink hindering the flow of ink and the smooth introduction of ink toward the ink-absorbing member 14.
Particularly, black ink is given a high solid content in order to increase the thickness of a character and has a property of being susceptible to an increase in viscosity and is likely to solidify when solvent contained in the ink has evaporated.
The black ink solidified on the slant surface hinders flow of black ink ejected subsequent to the solidified black ink, or flow of ink of another color.
Even if the slant member is not provided, black ink solidified within the ink-absorbing member hinders absorption of black ink ejected subsequent to the solidified black ink, or absorption of ink of another color.
Recently, an ink-jet recording apparatus has been required to have capability of producing a large volume of printed matter at high speed.
In order to meet this demand, a large amount of ink must be ejected during the cleaning and flushing operations performed for recovering the print capability of the recording head. Therefore, a large amount of waste ink cannot be discharged by an ink-jet recording apparatus in which the capping member performs a cleaning operation in conjunction with a flushing operation.
To prevent this problem, there has already been seen an ink-jet recording apparatus which is provided with an area designated specifically for flushing operation and which performs a flushing operation in the designated area.
A processing routine employed for the flushing operation comprises a step of deactivating a carriage motor within a predetermined flushing region and flushing a recording head, and a step of performing a print operation. As mentioned above, such a processing routine encounters a difficulty in increasing throughput.
For example, in the case of an ink-jet recording apparatus comprising a plurality of recording heads provided on a carriage, wherein the respective recording heads perform printing operation while traveling in the direction of their arrangement in a row, there must be ensured a flushing region whose width is equal to or greater than the width of the plurality of recording heads in the traveling direction of the carriage. Thus, the ink-jet recording apparatus cannot elude a further increase in size.